Display screen or portion thereof with a graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with a graphical user interface; and,

FIG. 2 is a front enlarged view of a portion of FIG. 1 (denoted in that figure with reference number 2).

The dash-dot broken lines show the display screen or portion thereof and form no part of the claimed design.

The dash-dash broken lines in the figures denote portions of the display screen or portion thereof with a graphical user interface that form no part of the claimed design. The dash-dash broken rectangular line indicated by the number “2” in FIG. 1 indicates a portion of FIG. 1 that is enlarged in FIG. 2 and forms no part of the claimed design. The wavy broken lines in the figures denote unclaimed boundaries of the display screen or portion thereof with a graphical user interface and form no part of the claimed design. The appearance of any portion of the display screen or portion thereof with a graphical user interface between the wavy broken lines forms no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with a graphical user interface, as shown and described. 